1. Field of the Invention
This invention relates to a travel assembly suited for arrangement on a vehicle such as a mining dump truck and having a travel motor and a planetary speed reduction mechanism for transmitting rotation of the travel motor at a lower rotational speed.
2. Description of the Related Art
As a conventional technology of this sort, there is one disclosed in Ciszak et al. U.S. Patent Application Publication No. 2004/0065169 A1. This conventional technology is provided with a travel motor, a planetary speed reduction mechanism for transmitting rotation of the travel motor at a lower rotational speed, a spindle forming an axle, a hub arranged on an outer side of the spindle and splined to the spindle, and a wheel supported on the hub via tapered roller bearings and rotatable by the planetary speed reduction system. The planetary speed reduction mechanism is provided with a sun gear rotatable by a shaft of the travel motor, planet gears for rotating the wheel in response to rotation of the sun gear, stepped pins forming rotary shafts for the planetary gears, a carrier supporting the stepped pins thereon and splined to the above-mentioned hub, and bolts fixedly securing the above-mentioned stepped pin on the carrier. The conventional travel assembly equipped with such a construction as described above is used for the rotational drive or the like of a tire of a mining dump truck.
With respect to the above-mentioned conventional technology, there is an outstanding desire for a construction that eliminates the hub splined to both the spindle and the planetary speed reduction mechanism with a view to increasing the strength of the spindle and cutting down the manufacturing cost, etc. To adopt such a non-hub construction as described above, it may be contemplated to directly spline the spindle and the carrier to each other. When constructed so, however, reaction force to rotation of a rotating member such as the wheel acts on a spline connection between the spindle and the carrier which are in mutually-micromovable relation. Namely, the spline connection repeats a micromovement while receiving reaction force, leading to a potential problem that the spline connection may undergo wearing and its durability may deteriorate. The issue is, therefore, to assure lubrication to the spline connection.